Nurbs

* Includes all updates from v5.0b1 to v5.0b7
* Added knot removal for spline volumes
* Added `operations.degree_operations` function for degree elevation and reduction (still WIP)
* Added more surface decomposition options to `operations.decompose_surface` function
* Minor coding improvements and fixes
* Documentation updates

* Fixed a critical bug in smesh and vmesh importers
* Added an option to change knot insertion and removal algorithms in the geometry classes
* Documentation updates

* Added `exchange.import_obj` function
* Added knot removal, degree elevation and degree reduction algorithms
* Simplified evaluator API to make implementations easier
* Added `knotvector` module
* Added surface trimming algorithm
* Minor bug fixes and compatibility updates
* Documentation updates

* Minor API updates and fixes
* Added more convenience methods to spline geometry classes
* Minor fixes and updates in `exchange` module
* Documentation updates
* Added volume support to dict-based import and exports, i.e. cfg, yaml, json
* Updated CI configurations
* Added CircleCI support for automation of deployment to PyPI, Anaconda Cloud and Docker Hub
* Updated TravisCI support to use tox and tox environments
* Updated AppVeyor support to generate Cython-compiled versions of geomdl as artifacts
* Added support for star imports, i.e. `from geomdl import *`

* Added `abstract.Geometry` and `abstract.SplineGeometry` classes
* Improved `multi` module reusability
* Added animate option to visualization component
* Minor bug fixes and staability improvements
* Documentation updates

* Added [Jinja2](http://jinja.pocoo.org/) template support to JSON, YAML and CFG importers
* Documentation updates and bug fixes